This invention relates generally to pump assemblies, and, more particularly, to drain pump assemblies for appliances.
Certain appliances, such as clothes washing machines and dishwashers, for example, include drain pumps for removing wash fluid from wash tubs in the appliances. The drain pump assembly is typically located below the tub so that water drains into the pump from the tub with gravity assisted action, and the pump assembly is activated to pump the fluid from a pump inlet to a pump outlet in communication with a discharge outlet of a building plumbing system. See, for example, U.S. Pat. Nos. 5,868,011 and 4,168,615.
More specifically, such a drain pump assembly typically includes an electric motor operatively coupled to a controller to activate and deactivate the pump assembly as desired. In operation, however, inlet pressure of the pump assemblies oscillates as suction is lost due to mixing of air and water in the tub, and due to sporadic flow of the wash fluid through a suction pipe. See, for example, U.S. Pat. No. 5,577,399.
Oscillations in pump inlet pressure, in turn, cause oscillations in the rotor assembly of the pump motor and results in pressure buildup within the pump motor. This oscillation of the rotor assembly and associated pressure effects have been found to dislodge motor bearings and adversely impact pump performance and operation, to create unpleasant noises in operation of the appliance, and to negatively impact appliance reliability and customer satisfaction.
In one aspect, a motor for a drain pump assembly is provided. The motor comprises a motor housing comprising a rotor chamber and a rotor assembly received in said rotor chamber. The rotor assembly comprises a rotor shaft received in said rotor chamber and supported therein on a bearing assembly. An end shield comprises a cavity for receiving an end of said rotor shaft and a pressure relief bore extending from said cavity to said rotor chamber.
In another aspect, a drain pump assembly for an appliance is provided. The drain pump assembly comprises a pump housing and a motor housing coupled to said pump housing, said motor housing comprising a rotor chamber therein. A rotor assembly is situated within said rotor chamber and comprises a rotor shaft, a bearing assembly, and a bushing surrounding said rotor shaft. An end shield extends over said rotor assembly, said end shield comprising a bearing cavity receiving said bushing, and a pressure relief bore in fluid communication with said rotor chamber and in fluid communication with said bearing cavity.
In a further aspect, an appliance comprises a cabinet, a tub within said cabinet, and a drain pump assembly for draining fluid from said tub. The pump assembly comprises a motor housing comprising a rotor chamber, and a rotor assembly coupled to said motor housing and comprising a rotor shaft, a bearing assembly, and a bushing surrounding said rotor shaft. An end shield comprises a bearing cavity receiving said bushing, and a pressure relief bore in fluid communication with said rotor chamber and in fluid communication with said bearing cavity.
In still another aspect, a drain pump assembly comprises a pump housing comprising an inlet, an outlet, and a pump chamber. A motor housing is coupled to said pump housing and comprises a rotabably mounted rotor assembly within a rotor chamber. The rotor assembly comprises a rotor shaft comprising a first end, a second end, and a bearing assembly. An impeller is mounted to said rotor first end and situated within said pump chamber, and an end shield comprises a bearing cavity inserted over said second end of said shaft and a pressure relief bore for relieving pressure in said bearing cavity as said rotor assembly oscillates in operation.